Polycrystalline diamond (PCD) compacts have a well-known use in industrial applications, such as drilling and/or cutting. As used herein, a PCD refers to a polycrystalline diamond that has been formed under high pressure, high temperature (HPHT) conditions. These compacts typically include polycrystalline diamond particles bonded into a coherent hard conglomerate. The diamond particle content of the compacts is high and there is an extensive amount of direct particle-to-particle bonding.
The compacts are made under HPHT conditions at which the abrasive particle is crystallographically stable. PCD compacts are most often formed by sintering diamond powder with a suitable binder-catalyzing by placing a cemented carbide substrate into the container of a press. A mixture of diamond particles or grains and binder-catalyst is placed atop the substrate and compressed under high HPHT conditions. In so doing, metal binder migrates from the substrate and sweeps through the diamond grains to promote a sintering of the diamond grains. As a result, the diamond grains become bonded to each other to form a diamond layer, and that diamond layer is bonded to the substrate along a planar or non-planar interface. Metal binder remains disposed in the diamond layer within pores defined between the diamond grains.
In the PCD compacts, the presence of the binder-catalyzing material in the interstitial regions adhering to the diamond particles leads to thermal degradation. Heat generated during use causes thermal damage to the PCD compact due to the difference in thermal expansion coefficients between the diamond particles, binder-catalyst material and the substrate.
To reduce thermal degradation, polycrystalline diamond compacts have been produced as preform PCD bodies for cutting and/or wear resistant elements, wherein the cobalt or other binder-catalyzing material is leached out from the continuous interstitial matrix after formation.
The acid leaching process of removing the binder-catalyzing material from polycrystalline diamond (PCD) body involves reactive acids and higher temperature of the acid-PCD contact region. The high temperature is critical for leaching the metal from the PCD. With conventional heating of acids, heat transfer takes place from the heat source to the acid bath and then to the PCD body. This phenomenon is slow and the temperature of the system is limited by the acid bath's boiling point.
In order to accelerate the rate of removal or leaching of the PCD compact direct heating of the PCD being leached by an external heat source is used. However, although leaching at the periphery surface of the PCD compact is adequate, the diffusion of acid to reactive sites deep within the PCD compact is limited. Accordingly, there is a need to increase the diffusion of acid into inner regions of the PCD compact, as well, as the diffusion of by-products from the inner reaction sites to improve leaching the PCD compacts.